In various branches of industry, substantially spherically shaped ferrite particles having a diameter up to 200 micrometers are used. Certain properties of these particles, such as low magnetic remanence, mechanical rigidity, surface hardness, and, if possible, spherical shape and homogeneity are critical for the application of these particles. A known method which is used for the manufacture of magnetized particles having a spherical shape is the melting of these particles in a stream of hot gases, for example, plasma, so that the particles may subsequently solidify and assume a substantially spherical shape.
The methods used in the prior art are, however, disadvantageous for various reasons. If a gas stream is used having a low enthalpy per unit of mass, or having a low latent heat, or the required dwelling time of the particles in the gas stream is too long, the particles which melt and are liquefied collide on the surface of the gas stream, and agglomeration results. As a result the precipitation of spherically-shaped particles is relatively small, and a separate mechanism must be employed with the gas stream to separate the agglomerated and non-agglomerated particles. For the same reasons, namely a low heat conductivity of the gases, the particles are cooled relatively slowly, and as a result, magnetically relatively harder particles are obtained. In view of the slow heating and cooling process, oxidizable gases in the vicinity of the gas stream penetrate to the center of the gas stream, and at least a portion of the ferrite particles are oxidized into a non-magnetic iron oxide. In order to obviate the above-noted disadvantages, the devices and methods known in the prior art require the use of a dense and costly protective gas.